McClintock, Murray; Ross, Pierre-Simon; White, James D. L.
(2009).
The importance of the transport system in shaping the growth
and form of kimberlite volcanoes
Lithos
, vol. 112
, nº S 1.
p. 465-472.
DOI: 10.1016/j.lithos.2009.04.014.
Résumé
Understanding the range of transport styles recorded by kimberlite deposits is key to describing the type and style of
eruptions. Building a clear picture of the processes that shape deposits is essential for selecting exploration targets and
evaluating the grade and value of diamond-bearing kimberlites. Variations in grade reflect differences in the diamond
content of different magma parcels erupted during the lifetime of the kimberlite volcano, sorting during transport of
eruption products, or re-working of diamonds during crater growth, cone collapse and erosion.
The form of the kimberlite volcano is largely determined when the magma arrives near the surface. If magma comes
into contact with external water, transport will be driven by a combination of magmatic gases + steam. From a diamond
exploration perspective, the resulting deep diatremes make the most attractive targets because they survive erosion and
form large geophysical anomalies. If water is too abundant, a tuff cone or tuff ring with no diatreme or a shallow one
will form. On the other hand, if external water is very limited or if the conduit is rapidly sealed by chilled melt, the
transport system will be driven by magmatic gases alone. The result will then be a spatter cone or cinder cone underlain
by a dike, possibly with a related lava flow, but with no diatreme.
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